Field of the Invention
The present invention relates to a stage apparatus, a lithography apparatus, and an article manufacturing method.
Description of the Related Art
A lithography apparatus transfers a desired pattern onto, for example, a substrate in a lithography step included in manufacturing steps for manufacturing articles such as semiconductor devices, liquid crystal display devices, and the like. An exposure apparatus which is an example of the lithography apparatus transfers (exposes) a pattern which has been formed in advance on an original (a reticle, a mask, or the like) onto a substrate on which a photoresist is coated (e.g., a wafer, a glass plate, or the like) via a projection optical system. Such an exposure apparatus includes a substrate stage that holds a substrate and is movable or an original stage that holds an original and is movable. In particular, in the substrate stage or the original stage with long stroke, a linear motor may be employed as a drive mechanism for generating a thrust force. If such a stage apparatus cannot perform normal operation due to some factors, action is taken to safely stop the stage by activating the dynamic brake (regenerative brake) within a linear motor. Japanese Patent Laid-Open No. 2001-85503 discloses a stage apparatus that safely stops a stage by activating a dynamic brake during a power failure.
In a stage apparatus which may be employed in a lithography apparatus, there is a stage apparatus having, for example, a coarse movement stage which operates (moves) with long stroke and a fine movement stage which enables fine adjustment such as precision positioning on the coarse movement stage, as a plurality of different movable units. There is also a stage apparatus having a main movable unit for holding a target object and a sub movable unit for supporting a mounting part such as wiring or a tube to the main movable unit as a plurality of different movable units.
Here, consider the case where the dynamic brake disclosed in Japanese Patent Laid-Open No. 2001-85503 is applied to a stage apparatus having such a plurality of movable units. For example, in the former stage apparatus, when the dynamic brake is activated upon high speed movement of the coarse movement stage, the coarse movement stage is decelerated sharply, resulting in a collision with a large shock between the coarse movement stage and the fine movement stage. The same applies to the case of the latter stage apparatus. Even when the main movable unit and the sub movable unit drive using the same linear motor the dynamic brake is activated, the braking force may not be the same due to a difference in mass or thrust force between the movable units. Consequently, the difference in relative speed between the movable units in the event of collision increases, so that the main movable unit may collide against the sub movable unit with a large shock. In contrast, it can also be contemplated that a braking force is designed to be extremely small so as to reduce the difference in relative speed between the movable units in the event of contact. If the braking force becomes small, the shock in the event of collision between the movable units can be reduced. However, although a shock absorber for mechanically receiving movable units is typically provided in a stage apparatus, a very long stroke is required to decelerate the movable units to a speed which can be handled by the shock absorption capability of the shock absorber. This may lead to an undesirable increase in size of the stage apparatus, which in turn results in an undesirable increase in size of the lithography apparatus in which the stage apparatus is employed.